How it works

In a normal HTTP type Axis situation, the AxisServlet is soley responsible for taking care of loading Axis. It uses the a WSDD file to configure the AxisEngine and provides an interface to that AxisEngine through HTTP requests.

However, in the AxisService we embed the AxisEngine (aka, the AxisServer) into an Avalon component. By doing so we are able to do two things. First, we are able to provide the AxisServer to the servlets as well as avalon components. There are classes in the org.apache.ivory.axis.servlet package which extend the Axis servlets so we can look up the AxisService and provide the servlets with the AxisEngine. Second, we are able to use the AxisEngine in our service to dynamically configure components as SOAP services. This is the real meat of the Axis component.

Internal Axis Configuration

Axis's primary mode of configuration resolves around WSDD deployment descriptors. Normally, the AdminServlet is the primary point of service deployment and undeployment using WSDD. The WSDD configuration model is somewhat intertwined all throughout Axis. While Axis starts to have its own internal configuration model, it fails in some respects.

The good news is that it is still workable to have a configuration model other than WSDD. If this wasn't possible you would have to deploy all your services through WSDD and wouldn't be able to dynamically expose them.

The AxisService uses the class org.apache.axis.configuration.SimpleProvider as its configuration model for the AxisServer. The SimpleProvider allows us to deploy services on the fly easily without resorting to WSDD.

Creating the service

The SOAPService class is fundamental to creating services dynamically with Axis. The javadocs have something good to say on this topic: A SOAPService is a Handler which encapsulates a SOAP invocation. It has an request chain, an response chain, and a pivot-point, and handles the SOAP semantics when invoke()d. This means the SOAPService is the central starting point for any service. It handles what happens when your service is invoked. However, a lot of the magic happens in the providers, detailed in the next section.

Axis Providers

Axis contains several default service handlers which encapsulate services. They are usually called "Providers." These providers are responsible for the actual instantiation of your java classes that the soap xml maps to (Serialization is handled by the TypeMapping and other org.apache.axis.encoding.* classes).

By setting the appropriate options on the SOAPService (which is the encapsulation of a SOAP invocation) we are able to create new services relatively easily (see DefaultAxisService). However, if we are exposing Avalon services we need to use a different provider other than the JavaProvider bundled with Axis. The AvalonProvider extends JavaProvider to do this. Instead of creating new objects, it just finds the object in the service manager.

Serialization

Currently, the AxisService relies solely on Bean(De)serializers to do the mapping from XML to the java class or component. Hopefully this will be made more flexible in the future. In the meantime, your SOAP Services must be in the java bean format and you can't hide anything from Axis. All methods are exposed.